Sledding system

ABSTRACT

A sledding system has a track including a support arrangement which defines a sledding path, and a plurality of glide elements which are carried by the support arrangement and extend along this path, each having an exposed face, with all of the exposed faces together forming a sledding surface. The glide elements are at least at the faces thereof of a first material having a low coefficient of friction. At least one sled is provided, having runners fromed with sledding-surface engaging portions of a second material which also has a low coefficient of friction but is different from the first material.

United States Patent Stiihmer 1 Sept. 30, 1975 [54] SLEDDING SYSTEM 2.942.557 6/1960 Hirsch 104 134 [76] Inventor: Rolfherbrt Sfiihmer, Aufdcn 3.690.265 9/1972 Honbata 104/70 2 2 ;2 3: 5 Bergen J01 Ehwtort' Primary Examiner-M. Henson Wood, Jr.

Axsisumt E.\'amincrD. W. Keen [2 1 Filcdl 1973 Attorney. Agent. or FirmMiehael S. Striker [21] Appl. No.: 409,102

[57] ABSTRACT [30] F i A li ti P i it D t A sledding system has a track including a support ar Oct 38 1972 German, U 2253055 rangcment which defines a sledding path, and a plural- June 18. 1973 Gcrman v 2330933 M glide clsmems which arc Carried by the Support arrangement and extend along this path, each having [52] Us CL 104/134; 104/691 272/565 an exposed face. with all of the exposed faces together [51] Int. 4 4 I H A636 21/00 forming a sledding surface. The glide elements are at [58] Field of Search H l04/69 70, 134 135. least at the faces thereof of a first material having a 272/565 low coefficient of friction. At least one sled is provided, having runners fromcd with sledding-surface [56] References Cited engaging portions of a second material which also has UNITED STATES PATENTS a low coefficient of friction but is different from the first material. 788.971 5/1905 Waters 104/134 1.356.794 10/1970 Smith 104/134 37 Claims, 6 Drawing Figures US. Patent Sept. 30,1975 Sheet 1 of 4 3,908,556

Sept. 30,1975 Sheet 2 of 4 3,908,556

Patent US. Patent Sept. 30,1975 Sheet 3 of4 3,908,556

n 0U a a y m 1,, MN mm 3 u cm 5 US. Patent Sept. 30,1975 Sheet40f4 3,988,556

SLEDDING SYSTEM BACKGROUND OF THE INVENTION The present invention relates generally to a sledding system, and more particularly to a novel sledding system which requires neither-ice nor snow for its operation.

The use of sleds has, of course, been known for a long time. Heretofore it has always been restricted to either the cold period of the year when ice or snow is available, or to areas where special snow making or ice making equipment was available to provide a track on which a sled could operate. However, there has been more and more of a demand for facilities on whichsledding could be persued even in the warm time of the year and without having to resort to snow machines, since aside from the considerable investment in purchasing these machines in the first place, it requires substantial expenditures to maintain the track usable by operation of these machines. This is especially true in the hot time of the year, when substantial amounts of energy must be expended to maintain a track snow covered or ice covered, and'even then it is not possible to avoid a dulling of the surface of the track due to the influence of the sun on the ice or snow.

It is already known to provide arrangements for socalled dry skiing, that is arrangements having tracks on which it is possible toski without having ice or snow covering the track. However, it has been found that these arrangements cannot be used for sledding purposes because the high-speeds and the substantial path lengths involved in sledding tracks cause excessive heating of these dry skiing tracks.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a novel sledding system which is capable of use without requiring the presence of. ice or snow on the sledding surface.

More particularly, it is an object of the present invention to provide such a novel sledding system which avoids the disadvantages of the prior art and makes it possible in a simple and economical manner to sled even in' the warm or hot periods of the year.

In keeping with the above objects, and with others which will become apparent hereafter, one feature of the invention resides in a sledding system which, briefly stated, comprises a track including support means defining a sledding path, and a plurality of glide elements carried by the support means extending along the path and'having exposed faces which together form a sledding surface, said glide elements being at least at the faces thereof of a first material having a low coefficient of friction; The system further comprises at least one sled having runners'provided with sledding-surface engaging portions of a second material which also has a low coefficient of friction but is different from the first.

material. r

The first material may be polyethylene, it may be fluoro-containing polyalkylene, it may bepolymethylenoxide, it may be polyester, melamine resin, or even cold rolled rust-free steel. Thesecond material may be fiuoro-containing polyalkylene, polymethylenoxide or polyethylene.

It is advantageous if theindividual glide elements each have a surface which is straight in the direction of elongation of the track, and whichis planar if the elements are intended for a straight track portion, and upwardly concave in the region of one lateral margin if the glide element is for a curved portion of the track, so as to simulate banking as is known from curves on roads. At least one side, and preferably both sides, of the track are provided with protective retaining barriers to prevent the sled or sleds rom leaving the track.

In accordance with a currently preferred embodiment, the first material may be a carbon-blackcontaining high-molecular low-pressure polyethylene, and the second material may be a polytetrafluorethylene filled either with finely divided metal powder, with carbon black, or with both powders. The metal powder may be a finely divided bronze powder. The carbon black or metal powder improves the heat dissipation.

According to a further embodiment the first material may be a polymethylenoxide which has been stabilized so as to be resistant to the elements, and the second material may again be polytetrafluoroethylene which is filled with finely divided metal powder and/or carbon black.

Of course, it will be appreciated that either or both of the first and second materials may be provided with additional conventional and well-known stabilizing and other materials in order to provide then with desired resistance to the elements, particularly sunlight, moisture and the effective ozone.

The first material also be a cold rolled austenitic chrome-nickel steel sheet, particularly of the type 4301 III D, and the second material may be carbon-blackfilled high-molecular low-pressure polyethylene, or polytetrafluoroethylene which is filled with a finely divided metallic powder and/or carbon black. The lowpressure polyethylene should have a molecular weight of at least 10. If chrome-nickel steel sheet is used, then the glide elements may be made self-supporting, so that they can be connected to the support structure without requiring an additional surface on which to rest.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS:

FIG. 1 is a somewhat diagrammatic cross-section through a sledding system according to the present invention in a straight track area;

FIG. 2 is a view similar to FIG. 1, but showing a track area for a right-hand curve;

FIG. 3 is a fragmentary longitudinal section (longitudinally of the track) for a portion of the track according to one embodiment;

FIG. 4 is a view similar to FIG. 3 illustrating a different embodiment;

FIG. 5 is a side view of a sled constituting a part of the novel system; and

FIG. 6 is a partially sectioned rear view of the sled.

DESCRIPTION OF THE PREFERRED EMBODIMENTS:

Discussing now the drawing in detail, and referring firstly to FIG. 1, it will be seen that this Figure illustrates a portion of the sledding system in a section taken through a straight track part. It will be seen that reference numeral 2 identifies a supporting surface on which a sledding surface 3 is provided, composed of a plurality of planar glide elements 4 which are each connected in their center region by a countersunk screw 35 with the support surface 2. The latter is provided on crossbars 9 which extend transversely to the elongation of the track, being spaced from one another in the longitudinal direction of the track and which in turn are connected to the upper side of two double-T rails 22 which extend in longitudinal direction of the track. The rails 22 in turn are connected by means of bolts or the like to transversely extending ties of wood or concrete, and holding element 12 are connected to the outer ends of these ties 10, having secured to them lateral supports 7 which are also connected with the crossbars 9 and which carry at the opposite lateral sides of the track respective barriers the inwardly facing sides of which are provided with glide layers 6.

FIG. 2 shows a track portion in a cross-section taken through a right-hand curve of the track. The track portion is identified with reference numeral 1 and again comprises double-T rails 11 mounted on the ties 10. In this case, however, there is provided a one-piece supporting surface 2' of metallic material, glass fiber reinforced synthetic plastic or a material available under the tradename Eternit. At the outer side of the curve the surface 2' is concavely shaped to simulate banking as it is found in a road, and it is found in a road, and is connected with the lateral supports 7 which are secured to the ties by means of the members 12. At the inner side of the curve there is provided the barrier 5 which has been previously described. Glide element 4' are provided on the supporting surface 2', extending transversely to the elongation of the track over the entire width of the latter and having at the inner side of the curve a planar portion 3a and at the outer side of the curve a concavely curved portion 3b.

The glide elements 4 can be mounted, particularly in the curved regions of the track, in the manner which is diagrammatically illustrated in FIG. 3. In this embodiment the glide elements 3 are configurated as stripshaped elements extending over the entire width of the track and provided at their transverse edges with recesses so as to form the steps 16. These reduced-height portions formed by the steps 16 extend into guide rails which are of U-shaped cross-section, so that between the transverse edges at the steps 16 and the upper portions 19 of the rails 17 which overlap them, as well as in the interior of the recess 18 in the rails 17, there will be sufficient play to permit for a thermal expansion or contraction of the glide elements 4. The individual elements 2' forming the support surface are mounted so that they define between one another small gaps 14. In the case of curved track portions the elements 2' and the elements 4 are provided with transverse edges which extend at an angle to the elongation of the track.

In the embodiment of FIG. 4 the glide elements 4' have surfaces which are slightly convex in the direction of the track, and their transverse edges are secured to the support surface 2 by means of countersunk screws 34 which hold retaining elements that overlap the lateral edges of the elements 4. This arrangement has the advantage that the sled will essentially glide only on the concave portions of the elements 4, so that the contact area between the sled runners and the elements 4 is correspondingly reduced, and the frictional resistance is similarly reduced. This embodiment is particularly suitable for straight-line track portions.

A sled 20 is illustrated in FIGS. 1, 5 and 6. Eventually, its construction corresponds to racing sleds which are used for bobsledding or the like. The runners 21 are inwardly inclined and connected with one another by metal brackets 22 to which transverse supports 23 are secured. The ends of these are connected with the longitudinal members 24, the latter having front ends which are displaceably guided in the upwardly inclined front end portions of the runners 21. This construction makes it possible for a user to shirt his weight, and by appropriate shifting and pulling on a guide strap or the like (not shown) the ends of which are connected to the tips of the runners 21, to influence the direction of travel of the sled.

In the particular illustrated embodiment of the sled turnable shafts 27 are provided in the rear regions of the two runners 21, at the outer side and being inclined relative to the central vertical plane of the sled at an inward angle. Arms 28 are pivotably mounted on these shafts 27 and carry at their rearward ends shafts 29 which extend parallel to the shafts 27 and on which guide wheels 30 are turnably journalled. Leaf springs 32 engage the arms 28 and press the wheels 30 which are provided with a cover 31 of rubber or synthetic plastic material elastically against the glide elements 4. The arrangement, dimensions, angle of inclination and material for the cover 31 should all be coordinated with the material used for the glide elements 4 themselves.

FIG. 6 shows particularly clearly that the glide profile 25 on the runners is of circular cross-section and is accommodated in an approximately semi-circular groove 36 of the respective runner 21. The front end of the glide profile 21 is provided with a head 41 of enlarged dimension which serves as an abutment and engages against that portion of the forward end portion of the runner 21 which surrounds the outlet opening of the groove 36. The rear end of the glide profile 25 is provided with a thread 43 onto which a nut 42 is threaded, which in turn engages the rear end face of the runner 21 about the rear opening of the groove 36. By appropriately tightening the nut 42 the profile 25 can be so tensioned in the groove 36 which follows the curvature of the runner 21, that it is reliably retained in this groove.

Depending upon the particular requirements, the groove 36 can also be undercut in its cross-section, and the glide profile 25 can be correspondingly undercut and inserted from one or the other open end of the groove 36 by sliding it into the same.

In the particular illustrated embodiment of FIG. 6 the circular cross-section of the glide element 25 has the advantage that by merely turning it about its longitudinal axis it can be tensioned in the groove 36 in various different positions, so that different surface portions of the glide element 25 can be exposed for contact with the glide elements 4.

In order to assure that the sled 20 can be stopped on the track whenever desired, a transverse shaft 35 is provided in the rearward metal bracket 22, having outwardly projected ends each of which carries a brake arm 39 the lower end of which is provided with a brake block 40 of rubber or another elastomeric material,

such as a synthetic plastic. Both of the arms 39 are con-- nected by the shaft 37 in such a manner that they can be pivoted only jointly, and not individually. Individual displacement might have the effect of throwing off the sled from a straight-line movement on the track, and causing it to be flung off the track. The upwardly extending end portions of the brake arms 39 are advantageously configurated as hand grips which can be engaged by a user. When the'user wishes to brake the sled 20, for instance when he encounters an unexpected obstruction on the track, it is merely necessary to engage one or the other of these hand grips and to pull on it, resulting in a pressing of the brake blocks 40 against the glide elements 4 and a rapid braking of the sled due to the resulting friction.

Of course, the sled could be configurated differently from what has been illustrated, for instance as a bobsled with steerable runners which are provided with glide elements.

The angle of inclination of the axis for the wheels 30, which latter serve merely as a guide function to guide the sled on the track, are advantageously inclined to the vertical central plane of the sled 20 at an angle of between substantially 5 and 30 inwardly and downwardly. These guide wheels 30 so stabilize the sled 20 on the track that even unskilled users, such as children, can sled along the entire track without any difficulties, and in particular without coming in contact with one or the other of the lateral safety barriers.

The particular material to be selected for the glid elements and for the surface engaging portions of the sled runner is selected in dependence upon the length, the inclination and the types of curves provided on the track. It will also be determined by the speed which it is desired to obtain, the wear behavior of the material and the manner in which the material will age, as well of course as by the expense of the material. It is, of course, desirable that the material be so-selected that even non-skilled users be able to obtain a sledding speed which is comparable to that which can be achieved by sledding on ice or snow. Tests have been carried out to attempt to determine the suitability of various materials, and it is found that many materials which afford sufficiently low friction if the track is short and the speed is low, cannot be used when in a sledding system according to the present invention where the track is to be long (for instance in excess of 500 meters) and the speeds are to be relatively high. The provision of the guide wheels 30 has been found not to disadvantageously influence the glide speed of the sled on the track.

It will be appreciated that the sledding system which has been described by way of one exemplary embodiment herein, can be varied in dependence upon particular requirements. The supporting structure and the like can be changed.

An advantage of having the gaps between adjacent ones of the support elements and glide elements is that water that might otherwise tend to accumulate due to rain or the like can readily run off. Any connecting or securing elements should of course be recessed or countersunk so as not to come in contact with the sledding-surface engaging portions on the runners of the in the curves may increase in height as the curve is entered and decreased as the curve is left, or it may be of constant height. The dimensioning of the glide elements and the support elements for them is advantageously so selected (considering the characteristics of their materials) that a sufficient lifetime is obtained for them and that no bulging or other distortion of the glide surface will occur.

In some circumstances it may be advantageous to provide the glide elements at the exposed faces thereof with a type of lubricant-pocket surface structure, and to supply such pockets at certain intervals with a lubricant. Such lubricants should of course be prefer ably of a type which will not stain the garments of a user if they should come in contact with such garments (e.g. due to a fall, trailing of a garment portion on the sledding surface, or the like). Moreover, the lubricants should not cause excessive and dangerous increase in the sledding speeds in the event the sledding surface should become moist. Depending upon the material used for the glide elements, the lubricant may be on a silicone basis, or it may be on a wax basis. It is preferred not to use lubricants, but if for any reason a lubricant is indeed used, it is very important as already outlinedthat it be so selected that in the presence of water (e.g. due to moisture on the track) the lubricant does not permit a significant increase in the sled speed.

It will be understood that each ofthe elements described above, or two or more together, may also find a useful application in other types of constructions differing from the types described above.

While the invention has been illustrated and described as embodied in a sledding system, it is not in tended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art farily constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims:

1. A sledding system, comprising a track including support means defining a sledding path, and a plurality of glide elements carried by said support means and having exposed faces which together form a sledding surface, said glide elements being at least at said faces of a first material selected from the group composed of polyethylene, fluoro-containing polyalkylene, polymethylene-oxide, polyester, melamine resin and coldrolled rust-free steel; and at least one sled having runners provided with sledding-surface engaging portions of a second material different from said first material and selected from the group composed of fluorocontaining polyalkylene, polymethyleneoxide and polyethylene.

2. A system as defined in claim 1, wherein said glide elements have edge portions extending transversely of said path, and adjacent ones of said edge portions of successive glide elements define narrow gaps with one another.

3. A system as defined in claim 1, wherein said support means comprises support elements having respective upwardly directed support surfaces; and wherein said glide elements are supported on said support sur faces.

4. A system as defined in claim 1, wherein some of said glide elements are for forming curves in said track, said some glide elements being of straight configuration but having at least one marginal portion extending transverse to said path and being inclined to the elongation thereof.

5. A system as defined in claim 1; and further comprising a retaining barrier extending along at least one lateral side of said track.

6. A system as defined in claim 5, said retaining bar rier having a face directed towards said one lateral side of said track; and further comprising a layer of a lowfriction material provided on said face of said retaining barrier.

7. A system as defined in claim 1, wherein said first material is carbon-black-filled high-molecular low pressure polyethylene, and said second material is carbon-black filled polytetrafluoroethylene.

8. A system as defined in claim 1, wherein said first material is carbon-black-filled high-molecular lowpressure polyethylene, and said second material is polytetrafluoroethylene filled with finely divided metal powder.

9. A system as defined in claim 1, wherein said first material is carbon-black-filled high-molecular lowpressure polyethylene, and said second material is polytetrafluoroethylene filled with finely divided metal powder and with carbon-black powder.

10. A system as defined in claim 1, wherein said first material is polymethyleneoxide stabilized to resist weather-caused deterioration, and said second material is polytetrafluoroethylene filled with finely divided powder selected from the group composed of carbonblack powder and metal powder.

1 l. A system as defined in claim 1, wherein said first material is cold-rolled austenitic chrome-nickel steel, and said second material is carbon-black-filled highmolecular low-pressure polyethylene.

12. A system as defined in claim 1, wherein said material is cold-rolled austenitic chrome-nickel steel, and said second material is polytetrafluoroethylene filled with finely divided powder selected from the group composed of carbon-black powder and metal powder.

13. A system as defined in claim 1, wherein said first material is cold-rolled austenitic chrome-nickel steel and said glide elements are constructed as load-bearing elements.

14. A system as defined in claim 1, wherein at least part of the sledding surface is substantially planar and formed by the exposed faces of planar glide elements.

15. A system as defined in claim 14, wherein the sledding surface comprises a lateral banking area formed by glide elements having concavely curved faces.

16. A system as defined in claim 1, wherein at least some of said glide elements extend transversely over the entire width of said track.

17. A system as defined in claim 16, wherein the exposed faces of at least sone of said glide elements have a planar main portion and a concavely curved lateral portion.

18. A sledding system, comprising a track including support means defining a sledding path, and a plurality of glide elements carried by said support means extending along said path and having exposed faces which together form a sledding surface, said glide elements being at least at said faces of a first material having a low coefficient of friction and having respective marginal portions which are spaced from one another; connecting means connecting said glide elements to said support means intermediate said marginal portions; and retaining means engaging said marginal portions and retaining them with freedom of limited movement resulting from expansion or contraction of said glide elements; and at least one sled having runners provided with sledding-surface engaging portions of a second material which also has a low coefficient of friction but is different from said first material.

19. A sledding system, comprising a track including support means defining a sledding path, and a plurality of strip-shaped glide elements carried by said support means extending along said path in direction transversely thereof and having exposed faces which together form a sledding surface, said glide elements being at least at said faces of a first material having a low coefficient of friction and having transversely extending spaced marginal portions; guide rail means engaging and retaining said marginal portions on said support means with freedom of limited movement relative to the support means due to expansion or contraction of said glide elements; and at least one sled having runners provided with sledding-surface engaging portions of a second material which also has a low coefficient of friction but is different from said first material.

20. A system as defined in claim 19, wherein at least one of said marginal portions of the respective glide el ement has a steppedrecess in the exposed face of said glide element; said guide rail means comprising guide rails which extend transversely to said path, being mounted on said support means and each having a slotshaped opening facing longitudinally of said path and partially receiving one of said marginal portions where the same is provided with said stepped recess.

21. A sledding system, comprising a track including support means for defining a sledding path, and a plurality of glide elements carried by said support means extending along said path and having exposed faces which together form a sledding surface and are slightly curved in direction of said track, said glide elements being at least at said faces of a first material having a low coefficient of friction; and at least one sled having runners provided with sledding-surface engaging portions of a second material which also has a low coefficient of friction but is different from said first material.

22. A system as defined in claim 21, wherein said exposed faces are slightly wavy in the direction of said track.

23. A sledding system, comprising a track including support means for defining a sledding path, and a plurality of glide elements carried by said support means extending along said path and having exposed faces which together form a sledding surface, said glide elements being at least at said faces of a first material having a low coefficient of friction; at least one sled having runners provided with sledding-surface engaging portions in form of discrete elements of a second material which also has a low coefficient of friction but is different from said first material; and connecting means for removably connecting said sledding-surface engaging portions with said runners of said sled.

2 3. A system as defined in claim 23, wherein said runners have grooves which extend longitudinally of therunners and in operation of the sled face said sledding surface; and wherein said engaging portions are in part received in the respective grooves.

25. A system as defined in claim 24, wherein said engaging portions also have parts extending out of said grooves and into contact with said sledding surface; and wherein said parts are convexly curvedv 26. A system as defined in claim 24, wherein said engaging portions are of circular cross-section.

27. A system as defined in claim 23, wherein said sled has a leading and trailing end, and said runners have front and rear end portions and are each provided with a groove extending from the respective front to the respective rear end portion; and wherein said engaging portions are received in the respective grooves and said connecting means connects said engaging portions with said runners only at said front and rear end portions and under tension.

28. A system as defined in claim 27, wherein said connecting means comprises a thread formed in the respective engaging portions, and a nut threaded onto said thread and abutting the associated runner at one of said front and rear end portions thereof.

29. A system as defined in claim 28, said sled having a leading and a trailing end; and further comprising guide wheels mounted on said sled in the region of said trailing end and engaging said sledding surface for guiding said sled on the same.

30. A system as defined in claim 29, wherein said guide wheels each comprise a wheel portion having a peripheral surface, a cover of friction-promoting material on said peripheral surface, and biasing means biasing said guide wheel so that said cover engages said sledding surface.

3i. A system as defined in claim 29, wherein said guide wheels are mounted for turning movement about axes which are inclined downwardly and inwardly with reference to a critical central longitudinal plane of said sled at an angle of between substantially 5 and 30.

32. A system as defined in claim 29, wherein said guide wheels are offset transversely of said sled with reference to said engaging portions.

33. A system as defined in claim 29, wherein said guide wheels are mounted for turning movement on shafts which are each carried by an arm. each of said arms in turn being pivotally mounted on a lateral surface of a respective runner.

34. A system as defined in claim 33, and further comprising biasing means acting upon the respective arms and permanently tending to pivot the same in a direction resulting in engagement of said guide Wheels with said sledding face.

35. A system as defined in claim 23; further compris ing a pair of arms located at opposite lateral sides of said sled and being pivotable about a common axis extending transversely to the elongation of said sled, each of said arms having a lower end portion; and further comprising a brake block carried by each of said end portions laterally adjacent the respective runners.

36. A system as defined in claim 35; further comprising a transversely extending shaft turnably mounted on the region of a trailing end of said sled and defining said common axis.

37. A sledding system comprising support means forming a sledding surface consisting of a material other than a material selected from the group composed of fluoro-containing polyalkylene, polymethyleneoxide and polyethylene, at least one sled having runners provided with sledding-surface engaging portions which are discrete elements and consist of a material selected from the group composed of fluorocontaining polyalkylene, polymethyleneoxide and polyethylene; and connecting means for removably connecting said sledding-surface engaging portions with 

1. A sledding system, comprising a track including support means defining a sledding path, and a plurality of glide elements carried by said support means and having exposed faces which together form a sledding surface, said glide elements being at least at said faces of a first material selected from the group composed of polyethylene, fluoro-containing polyalkylene, polymethylene-oxide, polyester, melamine resin and cold-rolled rust-free steel; and at least one sled having runners provided with sledding-surface engaging portions of a second material different from said first material and selected from the group composed of fluoro-containing polyalkylene, polymethyleneoxide and polyethylene.
 2. A system as defined in claim 1, wherein said glide elements have edge portions extending transversely of said path, and adjacent ones of said edge portions of successive glide elements define narrow gaps with one another.
 3. A system as defined in claim 1, wherein said support means comprises support elements having respective upwardly directed support surfaces; and wherein said glide elements are supported on said support surfaces.
 4. A system as defined in claim 1, wherein some of said glide elements are for forming curves in said track, said some glide elements being of straight configuration but having at least one marginal portion extending transverse to said path and being inclined to the elongation thereof.
 5. A system as defined in claim 1; and further comprising a retaining barrier extending along at least one lateral side of said track.
 6. A system as defined in claim 5, said retaining barrier having a face directed towards said one lateral side of said track; and further comprising a layer of a low-friction material provided on said face of said retaining barrier.
 7. A system as defined in claim 1, wherein said first material is carbon-black-filled high-molecular low-pressure polyethylene, and said second material is carbon-black filled polytetrafluoroethylene.
 8. A system as defined in claim 1, wherein said first material is carbon-black-filled high-molecular low-pressure polyethylene, and said second material is polytetrafluoroethylene filled with finely divided metal powder.
 9. A system as defined in claim 1, wherein said first material is carbon-black-filled high-molecular low-pressure polyethylene, and said second material is polytetrafluoroethylene filled with finely divided metal powder and with carbon-black powder.
 10. A system as defined in claim 1, wherein said first material is polymethyleneoxide stabilized to resist weather-caused deterioration, and said second material is polytetrafluoroethylene filled with finely divided powder selected from the group composed of carbon-black powder and metal powder.
 11. A system as defined in claim 1, wherein said first material is cold-rolled austenitic chrome-nickel steel, and said second material is carbon-black-filled high-molecular low-pressure polyethylene.
 12. A system as defined in claim 1, wherein said material is cold-rolled austenitic chrome-nickel steel, and said second mAterial is polytetrafluoroethylene filled with finely divided powder selected from the group composed of carbon-black powder and metal powder.
 13. A system as defined in claim 1, wherein said first material is cold-rolled austenitic chrome-nickel steel and said glide elements are constructed as load-bearing elements.
 14. A system as defined in claim 1, wherein at least part of the sledding surface is substantially planar and formed by the exposed faces of planar glide elements.
 15. A system as defined in claim 14, wherein the sledding surface comprises a lateral banking area formed by glide elements having concavely curved faces.
 16. A system as defined in claim 1, wherein at least some of said glide elements extend transversely over the entire width of said track.
 17. A system as defined in claim 16, wherein the exposed faces of at least sone of said glide elements have a planar main portion and a concavely curved lateral portion.
 18. A sledding system, comprising a track including support means defining a sledding path, and a plurality of glide elements carried by said support means extending along said path and having exposed faces which together form a sledding surface, said glide elements being at least at said faces of a first material having a low coefficient of friction and having respective marginal portions which are spaced from one another; connecting means connecting said glide elements to said support means intermediate said marginal portions; and retaining means engaging said marginal portions and retaining them with freedom of limited movement resulting from expansion or contraction of said glide elements; and at least one sled having runners provided with sledding-surface engaging portions of a second material which also has a low coefficient of friction but is different from said first material.
 19. A sledding system, comprising a track including support means defining a sledding path, and a plurality of strip-shaped glide elements carried by said support means extending along said path in direction transversely thereof and having exposed faces which together form a sledding surface, said glide elements being at least at said faces of a first material having a low coefficient of friction and having transversely extending spaced marginal portions; guide rail means engaging and retaining said marginal portions on said support means with freedom of limited movement relative to the support means due to expansion or contraction of said glide elements; and at least one sled having runners provided with sledding-surface engaging portions of a second material which also has a low coefficient of friction but is different from said first material.
 20. A system as defined in claim 19, wherein at least one of said marginal portions of the respective glide element has a stepped recess in the exposed face of said glide element; said guide rail means comprising guide rails which extend transversely to said path, being mounted on said support means and each having a slot-shaped opening facing longitudinally of said path and partially receiving one of said marginal portions where the same is provided with said stepped recess.
 21. A sledding system, comprising a track including support means for defining a sledding path, and a plurality of glide elements carried by said support means extending along said path and having exposed faces which together form a sledding surface and are slightly curved in direction of said track, said glide elements being at least at said faces of a first material having a low coefficient of friction; and at least one sled having runners provided with sledding-surface engaging portions of a second material which also has a low coefficient of friction but is different from said first material.
 22. A system as defined in claim 21, wherein said exposed faces are slightly wavy in the direction of said track.
 23. A sledding system, comprising a track including support means for defining a sledding path, and A plurality of glide elements carried by said support means extending along said path and having exposed faces which together form a sledding surface, said glide elements being at least at said faces of a first material having a low coefficient of friction; at least one sled having runners provided with sledding-surface engaging portions in form of discrete elements of a second material which also has a low coefficient of friction but is different from said first material; and connecting means for removably connecting said sledding-surface engaging portions with said runners of said sled.
 24. A system as defined in claim 23, wherein said runners have grooves which extend longitudinally of therunners and in operation of the sled face said sledding surface; and wherein said engaging portions are in part received in the respective grooves.
 25. A system as defined in claim 24, wherein said engaging portions also have parts extending out of said grooves and into contact with said sledding surface; and wherein said parts are convexly curved.
 26. A system as defined in claim 24, wherein said engaging portions are of circular cross-section.
 27. A system as defined in claim 23, wherein said sled has a leading and trailing end, and said runners have front and rear end portions and are each provided with a groove extending from the respective front to the respective rear end portion; and wherein said engaging portions are received in the respective grooves and said connecting means connects said engaging portions with said runners only at said front and rear end portions and under tension.
 28. A system as defined in claim 27, wherein said connecting means comprises a thread formed in the respective engaging portions, and a nut threaded onto said thread and abutting the associated runner at one of said front and rear end portions thereof.
 29. A system as defined in claim 28, said sled having a leading and a trailing end; and further comprising guide wheels mounted on said sled in the region of said trailing end and engaging said sledding surface for guiding said sled on the same.
 30. A system as defined in claim 29, wherein said guide wheels each comprise a wheel portion having a peripheral surface, a cover of friction-promoting material on said peripheral surface, and biasing means biasing said guide wheel so that said cover engages said sledding surface.
 31. A system as defined in claim 29, wherein said guide wheels are mounted for turning movement about axes which are inclined downwardly and inwardly with reference to a critical central longitudinal plane of said sled at an angle of between substantially 5* and 30*.
 32. A system as defined in claim 29, wherein said guide wheels are offset transversely of said sled with reference to said engaging portions.
 33. A system as defined in claim 29, wherein said guide wheels are mounted for turning movement on shafts which are each carried by an arm, each of said arms in turn being pivotally mounted on a lateral surface of a respective runner.
 34. A system as defined in claim 33, and further comprising biasing means acting upon the respective arms and permanently tending to pivot the same in a direction resulting in engagement of said guide wheels with said sledding face.
 35. A system as defined in claim 23; further comprising a pair of arms located at opposite lateral sides of said sled and being pivotable about a common axis extending transversely to the elongation of said sled, each of said arms having a lower end portion; and further comprising a brake block carried by each of said end portions laterally adjacent the respective runners.
 36. A system as defined in claim 35; further comprising a transversely extending shaft turnably mounted on the region of a trailing end of said sled and defining said common axis.
 37. A sledding system comprising support means forming a sledding surface consisting of a material other than a material selected from the grOup composed of fluoro-containing polyalkylene, polymethyleneoxide and polyethylene, at least one sled having runners provided with sledding-surface engaging portions which are discrete elements and consist of a material selected from the group composed of fluoro-containing polyalkylene, polymethyleneoxide and polyethylene; and connecting means for removably connecting said sledding-surface engaging portions with said runners of said sled. 